Method of and device for testing a photographic film

ABSTRACT

The invention concerns a method of testing the state of development of a photographic film in a light-proof cartridge. According to the invention, the leading edge of the film is pulled out of the cartridge, the film is positioned between a light source and a photosensor, and the amount of light passing between the light source and photosensor is measured. The state of the film is recognized as being undeveloped if a small amount of light passes therebetween.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for testing thestate of development of a photographic film, the major portion of whichis disposed in a light-proof cartridge but which has a leading end thatextends out of the cartridge.

When photographic films are processed in large laboratories, the filmsare removed from the film cartridges in what is called a splicer andcemented together into a long strip. To do this, the trailing end of onefilm and the leading end of the subsequent film are positioned in acementing station in such a way that the ends of the respective filmscan be joined together with a strip of adhesive. Devices of this genusare described in German Published Application No. 3,833,468 and EuropeanPublished Application No. 0,212,134, for example. The positioning of thefilms in the splicing station is usually carried out by means ofinfrared-light barriers.

U.S. Pat. No. 5,093,686 describes a film system and a laboratoryorganization wherein the film, after being developed and printed, isrewound back into the cartridge and returned to the customer within theoriginal cartridge along with the finished prints. However, this leadsto the problem that the laboratory cannot be certain whether a filmcartridge that has been delivered to them contains a film that has notyet been developed or an already developed film from which only repeatorders are to be filled.

A splicer that is suitable for such films can be used in darkroomoperation, as has been common in the past, to cement the unexposed filmsinto a strip that is then developed in a developing machine. Such asplicer can, however, also be used in a similar way in lightroomoperation to splice together into a strip films that repeat orders areto be filled from, whereupon, however, the strip is not to be developed,but printed. If an error occurs during the sorting of incoming filmcartridges, such that, for example, a film that has previously beendeveloped is processed with the as-yet undeveloped films or vice-versa,it can lead to the destruction of the incorrectly sorted film. Whereas afilm that has already been developed will fade severely when it isdeveloped again, an as-yet unprocessed film that has been mistakenlyincluded with the previously developed films will be exposed as theresult of being processed in the lightroom-operation splicer andaccordingly completely ruined.

The U.S. Pat. No. 5,521,662 (not a prior publication) discloses acamera. The description mentions an infrared-transmitting sensor thatemploys various transmission rates to determine whether the film hasbeen developed.

SUMMARY OF THE INVENTION

A principal object of the present invention is therefore to provide amethod of and device for reliably determining very early on in thelaboratory whether a particular film has or has not been developed.

This object, as well as other objects which will become apparent fromthe discussion that follows, are achieved, in accordance with thepresent invention, by positioning the leading end of the film, whichextends out of the cartridge, between the source of light and aphotosensor; detecting the presence of the film and measuring thetransmission of light between the source of light and the photosensor.The state of the film's development is determined by comparing theresult of the detection of the presence of the film with that of themeasurement. The point of departure for the invention is that adeveloped film is practically completely transparent, especially in theinfrared range of the spectrum, where most standard light-barriermodules operate. It is accordingly impossible with such aninfrared-transmitting light barrier to determine whether there is analready developed film or no film at all between the light source andthe photosensor. Another detector must accordingly be employed todetermine whether or not there is a film in the film guide. Only oncethis has been confirmed can an infrared light barrier be employed todetermine whether the film is transparent or opaque to infrared light.In the former instance it is a developed film and in the latter, anundeveloped one. The presence of the film can for example be verifiedwith a mechanical sensor mounted such that the leading end of the filmwraps around a switch lever. Since, however, this could cause scratcheson the film under some conditions, a pneumatic approach is to bepreferred. In this approach an air nozzle can be aimed at the film guideand the pressure measured. This pressure will increase abruptly when afilm is directly in front of the nozzle's opening. It would also bepossible to position an air-pressure sensor on the other side of thefilm guide to measure the reduction of pressure when a film is travelingbetween the nozzle and the pressure sensor. A heat-sensitive electricresistor, a resistor, that is, with a resistance that varies withtemperature, could alternatively be employed instead of a pressuresensor. When a film is in the guide and no air is blowing against such aresistor, the temperature of the component will increase and itsresistance will vary accordingly.

Since the film described in U.S. Pat. No. 5,093,686 for example has amagnetic coat, it is also possible to detect the presence of a firm witha magnetism-detecting head.

It is preferable to determine the presence of a film with a reflectedinfrared-light barrier. This reasonably priced standard component can bepositioned to direct light against the reflective rear surface of thefilm. With this light barrier it is possible to also detect developedfilms, which are in themselves infrared-transparent.

Once it has been definitely determined that a film is in the guide, atransmitted infrared-light barrier can be employed to determine whetherthe film has already been developed. In this event, the two possiblestates "transparent" and "opaque" are adequate for the determination.

It is, however, also possible to determine the state of development of afilm with only one light barrier using light in the green or bluewavelength range (420-580 nm). A particularly appropriate source oflight in this event is an LED that emits light at a wavelength of 569nm. It is possible at this range to definitely distinguish between thethree possible states "no film", "undeveloped film", and "developedfilm". While a nearly 100% transmission of light will be measured in the"no film" state, an undeveloped film will block almost all the light, sothat no transmission of light can be measured. A developed film willvery definitely be in the range between these two extremes, so that allthree states can be well differentiated. Further details and advantagesof the present invention will be evident from the subsidiary claims andfrom a description of one embodiment by way of example, which will nowbe comprehensively explained with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of controls that employ twodetectors.

FIG. 2 is a schematic illustration of controls that employ a lightbarrier.

FIG. 3 illustrates a film guide provided with a reflected infrared-lightbarrier and with a transmitted infrared-light barrier.

FIG. 4 is a block diagram of a state-detecting system employing twosensors.

FIG. 5 is another block diagram of a state-detecting system employingtwo sensors.

FIG. 6 is a block diagram of a state-detecting system employing only onesensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sensor 1 in FIG. 1 is preferably the photodiode of a reflectedinfrared-light barrier with a threshold switch designed such that therewill be signal present at its input terminal 4 only when the presence ofa film in the film guide has been confirmed. Although the light barrierassigned to sensor 2 also operates in the infrared range, it is, incontrast to the reflected infrared-light barrier, designed as atransmitted infrared-light barrier. The threshold switch in sensor 2 isdesigned such that no signal is present at its input terminal 5 whenthere is an undeveloped film in the film guide. Controls 3 have twoinput terminals, an input terminal 4 connected to sensor 1 and an inputterminal 5 connected to sensor 2. The controls are also provided withoutput terminals 6, 7, and 8, which can be employed for specific controlpurposes. These output terminals are actuated by logic stages 9 and 10.

FIG. 3 illustrates a film guide with an associated sensing system. Film12 is advanced through a guide 14 in the direction indicated by arrow Aby an unillustrated transport system. A reflected-light barrier 23comprises a source 21 of light and a photosensor 1, both on the sameside of film guide 14. Photosensor 1 consequently receives light onlywhen the light emitted by source 21 is reflected by film 12. Atransmitted-light barrier 24 comprises a source 22 of light and aphotosensor 2 on opposite sides of the film guide 14. Here, photosensor2 emits a signal either when there is no film 12 in guide 14 and thelight emitted by source 22 reaches sensor 2 directly or when there is analready developed and accordingly infrared-transparent film in theguide.

The logic stage 9 in the controls 3 illustrated in FIG. 1 is designedsuch that voltage will be applied to output terminal 6 when no signal ispresent at input 4. As will accordingly be evident from FIG. 3, thismeans that no film 12 is present in guide 14, or at least that theleading edge 13 of a film 12 has not yet arrived in the vicinity ofreflected-light barrier 23.

Light will, however, strike photosensor 1 as soon as film does arrive inthis region, and voltage will accordingly be present at input terminal4. Logic stage 9 will now divert the voltage previously present atoutput terminal 6 to a connection 11 to logic stage 10. Logic stage 10is connected to the photosensor 2 in transmitted-light barrier 24 byinput terminal 5.

If the film 12 illustrated in FIG. 3 has already been developed,photosensor 2 will receive the light emitted by source 22, becausedeveloped films are practically transparent in the infrared range. Inthis case, a signal will accordingly be present at input terminal 5. Iflogic stage 10 is accordingly provided with a signal by way ofconnection 11 and input terminal 5, there will also be a signal atoutput terminal 7 but no signal at output terminals 6 and 8. If the film12 is undeveloped and will accordingly have a blocking effect in theinfrared range, the photosensor 2 will receive no light and there willbe no signal at input terminal 5. In this event (a signal at connection11 but no signal at input 5), there will be a signal at output terminal8. In this state there will be no signal at output terminals 6 and 7.

Controls 3 can be considered a logical component with two input andthree output terminals. To ensure unambiguous results here,transmitted-light barrier 24 will be ideally positioned where it can acton the edge of the film 12 opposite the reflected-light barrier 23. Theswitching logic of 3 can be derived from the following table, wherein an"x" represents the presence of signal and an "o" the absence of asignal.

    ______________________________________                                        Input  Input    Output   Output Output                                        terminal                                                                             terminal terminal  terminal                                                                            terminal                                      4              5                                                                                    6               8                                                                                  State                              ______________________________________                                        x      ∘                                                                          ∘                                                                          ∘                                                                        x      Film                                                                               undeveloped                       ∘                                                                            x          x        ∘                                                                     ∘                                                                      No film                                                                           present                           x              x                                                                                   ∘                                                                          x      ∘                                                                    Film                                                                              developed                         ______________________________________                                    

The embodiment illustrated in FIG. 2 has only one detector, whichemploys a photosensor 30 operating in the blue-green wavelength rangeand emitting a signal proportional to the light incident to it. Controls33, again have three output terminals 36, 37, 38 and accordingly only asingle input terminal 34. Controls 33 also include two referencegenerators 35 and 39 and comparator stages 31 and 32. The signal emittedby reference generator 35 represents approximately 90% of the signalpresent at input terminal 34 when there is no film in guide 14. Thesignal emitted by reference generator 39 represents approximately 10% ofthat signal. Both references can always be adjusted in accordance withthe changing output of the detector's source of light.

If the signal present at input terminal 34 is more powerful than thesignal emitted by reference generator 35, there will be a signal atoutput terminal 36. If the signal present at input terminal 34 is weakerthan the set-point value, a signal is switched to connection 40. In thisevent there will also be a signal at the output terminal of comparatorstage 32 because the signal obtained from connection 40 will also bemore powerful that the signal emitted by reference generator 39. ANDstage 42 will accordingly also obtain a signal from comparator stage 32,whereas there will be no signal from NOT stage 41. There willaccordingly also be no signal at output terminal 37. Output terminal 38will also have no signal by way of NOT stage 43.

If there is a developed film in the film guide, the signal at inputterminal 34 will be weaker than the signal emitted by referencegenerator 35 but more powerful than the signal emitted by referencegenerator 39. No signal will accordingly be forwarded to output terminal36, although a signal will be present at the output terminal ofcomparator stage 32. Since a signal from NOT stage 41 will be present atAND stage 42, the latter will forward a signal to output terminal 37.There will again be no signal from NOT stage 43 at output terminal 38.

When there is an undeveloped film in the film guide, the signal at inputterminal 34 will be weaker than the signal emitted by referencegenerator 39. Whereas the situation at the output terminal of comparatorstage 31 will accordingly be unchanged, there will no longer be anysignal at the output terminal of comparator stage 32, and accordingly nosignal at output terminal 37 either, although a signal will have arrivedat output terminal 38 by way of NOT stage 43.

To represent the embodiment illustrated in FIG. 3 it will be necessaryto eliminate detector 23. The source 22 of light in detector 24 must nowbe capable of emitting light in the blue-green wavelength range

Since a still undeveloped film is sensitive to light within that rangeand since a latent image of the source of light would be produced on afilm tested with a device in accordance with the present embodiment, itwould be of advantage to design the source to produce a particularpattern on the film. A laboratory could for example consequently exposean identifying mark onto the leading edge of the film.

The circuits illustrated in FIGS. 1 and 2 could also be realized in theform of software in accordance with the programs illustrated in FIGS. 4through 6. In this event, the signal 51 emitted by sensor 1 andillustrated in FIG. 4 will be polled. As long as the sensor is emittingno signal, the program will be repeated. Once a signal 51 is detected,the signal 52 emitted by sensor 2 will also be polled. The absence of asignal 52 indicates the presence of a developed film in film guide 14.This decision is represented by reference number 57. A signal at sensor2 on the other hand will indicate that the detected film is has not yetbeen developed. The decision is undertaken at reference number 58.

It is alternatively possible for sensor 2 to be polled first, asrepresented by reference FIG. 52 in FIG. 5. If there is no signal atsensor 2, the presence of an undeveloped film can be immediately decidedat 58. If, on the other hand, a signal is present, sensor 1 will bepolled again at reference number 51. If no signal is present, no filmhas at least as yet arrived in the sensor's vicinity. The program isaccordingly reset and the polling begins anew. If, on the other hand,there is a signal at sensor 1, a decision can now be made at 57 that adeveloped film is present.

The block diagram in FIG. 6 represents a device with a sensor and asource of blue-green light. A test is conducted at reference number 55to determine whether the signal at sensor 2 is more powerful than thethreshold, which constitutes about 90% of the signal at sensor 2 whenthere is no film in the film guide. The signal at sensor 2 being morepowerful than the threshold indicates that there is no film in the filmguide, and the program is reset. If, on the other hand, the signal atsensor 2 is weaker, it is compared with another threshold at referencenumber 59. This threshold will constitute only 10% of the signal atsensor 2 as long as there is no film in the film guide. If the signal ismore powerful than the threshold, it is decided at 57 that a developedfilm is present. If the signal is weaker, on the other had, the decisionat 58 indicates an undeveloped film.

Various responses can now occur with respect to the confirmed states 57and 58 or to the signals at output terminals 7 and 8 or 37 and 38. Ifthe testing device is part of a splicer that splices undeveloped filmsinto a long strip so that they can be fed through processing apparatus,the decision "developed film" will initiate rewinding of the film backinto the cartridge and closing of the light flap. An appropriate messagemust also be communicated to the operator that an already developed filmhas been erroneously loaded. The same response must be triggered inprocessing apparatus that only develops single films obtained from acartridge.

If the splicer has been set to process re-orders whereby alreadydeveloped films have been spliced into a long strip, the "undevelopedfilm" confirmation must trigger a particular response. In this event,the film must be immediately rewound into the cartridge, because thelatent images would be destroyed when exposed to light.

The method and device in accordance with the present invention can beapplied not only to the equipment mentioned herein but also in anyapplication where incorrect handling of film, developed or not, couldresult in irreparable loss to the customer.

There has thus been shown and described a novel method and device fortesting a photographic film which fulfills all the objects andadvantages sought therefor. Many changes, modifications, variations andother uses and applications of the subject invention will, however,become apparent to those skilled in the art after considering thisspecification and the accompanying drawings which disclose the preferredembodiments thereof. All such changes, modifications, variations andother uses and applications which do not depart from the spirit andscope of the invention are deemed to be covered by the invention, whichis to be limited only by the claims which follow.

What is claimed is:
 1. A method of testing the state of development of aphotographic film in a light-proof cartridge, comprising the steps ofpositioning the leading end of the film, which extends out of thecartridge, between a source of light and a photosensor, detecting thepresence of the film, and measuring the transmission of light betweenthe source of light and the photosensor.
 2. Method as recited in claim1, wherein the presence of a film is detected with a second detector andthe state of the film's development is determined by comparing theresult of that detection with that of the measurement.
 3. Method asrecited in claim 2, wherein the presence of a film is detectedmechanically.
 4. Method as recited in claim 2, wherein the presence of afilm is detected with a reflected infrared-light barrier.
 5. Method asrecited in claim 4, wherein the reflected infrared light barrier ispreferably directed at a surface opposite an emulsion side of the film.6. Method as recited in claim 2, wherein the measurement is carried outwith a transmitted infrared-light barrier.
 7. Method as in claim 1,wherein the transmission of light in the green and/or blue wavelengthrange is measured and the presence of a film is detected and the stateof a present film's development determined from how much light istransmitted.
 8. Method as recited in claim 2, wherein the presence of afilm is detected pneumatically.
 9. A device for testing the state ofdevelopment of a photographic film disposed in a light-proof cartridge,said device comprising a detector for detecting the presence of a film,a source of light and a photosensor for measuring the transmission oflight through a section of the film extending out of the cartridge, andcontrol means connected to the photosensor for detecting the presenceand state of development of the film on the basis of the incomingsignals.
 10. Device as recited in claim 9, wherein the control means iscoupled to the detector and is operative to detect the followingstates:state a: no film present, or state b: film present from thesignal leaving the detector, and state c: much light transmitted orstate d: little light transmitted from the signal leaving thephotosensor and, in the event that states b and c are detected, torecognize the presence of a developed film and, in the event that statesb and d are detected, to recognize the presence of an undeveloped film.11. Device as recited in claim 9, wherein the source of light is asource of infrared light.
 12. Device as recited in claim 10, wherein thedetector includes a reflected infrared-light barrier.
 13. Device asrecited in claim 9, wherein the source of light emits light in the blueand/or green wavelength range and wherein the control means is operativeto compare the signal leaving the photosensor with prescribed thresholdsand differentiates between the following states:state 1: no film presentstate 2: developed film present, and state 3: undeveloped film present.